Zachary Elliott
@zaelefty
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Sex difference research in biology. Producer of animated videos, articles, and books on sex and gender. Founder of @PdxInstitute .
United States
Joined August 2014
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I present my new book on debunking the sex spectrum!
Order now on Amazon!
I tackle 10 common sex spectrum arguments and teach the reader how to respond with detailed knowledge from evolutionary and developmental biology literature.
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The strength difference between male and female bodies is vast.
On average, males have:
- 57% more grip strength [1]
- 65% more leg strength [2]
- 90% more total upper body strength [3]
- 162% more punch power [4]
To put these numbers in comparison, males are only 7%
Opinion: Trans women aren’t a threat to women’s sport contrary to British Rowing’s new policy
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If man and woman are social constructs, then why do you need hormones and surgery to align with a social construct?
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@IanCopeland5
Many fish can switch sex, yes. This reinforces the binary because they only ever switch from male to female or female to male. There is no third or additional sex they can switch to. It’s therefore not a spectrum.
Furthermore, humans are not sequential hermaphrodites. We are
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There's 5 lies that trans-identified male Veronica Ivy utilizes in this clip about biological sex and sport. Let's break it down.
1. "Policing whether transgender women and intersex women are really female is built in racism."
While there has been historical racism against
The transgender self-imposed struggle session that Trevor Noah is undergoing here is priceless. He knows men aren’t women, squirms and squirms.
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@CaptAmazo
The shedding of the uterine lining IS the period.
The cause is the hypothalamic-pituitary-ovarian (HPO) hormonal axis interacting with the uterus to induce the shedding. Only females can have this.
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And yet, curiously, males produce 15-20 times more testosterone than females.
The gap is so large in fact, that the highest T levels in females are still 5 times lower than the lowest T levels in males.
So, while T is present in both males and females, it is in far different
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Dylan Mulvaney is not trans. He’s literally a trained actor who’s found a way to get attention.
His “Day X of being a girl” series is a never-ending list of heavily caricatured jokes about sex stereotypes. This is not a serious person with gender dysphoria.
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A trans activist asked me, “If we exclude trans women from female sports, why not black women too?”
Aside from how racist this is, it couldn’t be more scientifically wrong.
Black women DO NOT go through male puberty. They go through female puberty, because they’re female! 🤦♂️
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The male sex is the phenotype that produces sperm.
The female sex is the phenotype that produces eggs.
This definition is so consistent that it applies to every single plant and animal species with a male-female sexual system.
This is why it’s the universal definition.
@EBurke_5
@CBtn13
@JamesEsses
There is not one consistent definition of male or female sex. Not in humans, not in any other animal.
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Lots of respect for how JK Rowling continues to stand up to the bullies, abusers, and gaslighters.
War is Peace.
Freedom is Slavery.
Ignorance is Strength.
The Penised Individual Who Raped You Is a Woman.
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@IanCopeland5
Those are karyotypes, a person's chromosome profile, not genotypes, which is the full genetic (gene) profile.
This is basic stuff that a geneticist like you should already understand at undergrad or high school level way before getting a PhD.
Each of those karyotypes results
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This myth needs to end: we all start out as females in the womb.
No, we all begin phenotypically indifferent (undifferentiated).
In the embryo, the gonads begin bipotential (they differentiate into testes or ovaries based on genetic triggers), and the fetus has the primordial
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A woman’s Menstrual Cycle is controlled through the hormonal feedback loop between the hypothalamus, pituitary gland, ovaries, and uterus.
Males on cross-sex hormones do not have periods because they do not have a uterus or ovaries, and therefore there is no feedback loop
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Why does a male’s feelings matter more than the rights of female athletes to fair competition, safety, and dignity?
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It is often claimed by gender activists that 1.7% of the population are neither male nor female.
But 88% of the 1.7% number involves Late Onset CAH, which involves unambiguous males or females who are almost always fertile.
This drops the number to 0.2%. But even within this
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@laurahelmuth
@audubonsociety
White-throated sparrows have two sexes with four unique chromosome combinations.
The “four chromosomally distinct sexes” produce either sperm or eggs, not a third or fourth gamete type.
Thus, just two sexes, which the paper also reaffirms.
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Many fish can switch sex, yes. This reinforces the binary because they only ever switch from male to female or female to male. There is no third or additional sex they switch to. It’s therefore not a spectrum.
Furthermore, humans are not sequential hermaphrodites. We are
Sex (like all traits) is not binary. Gender (which is a social construct ) is not binary.
All traits are on a spectrum. Many species of fish change their sex regularly.
Sex is no exception to the rules of biology, just because you are a bigot...
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I had a discussion yesterday with an 18 year old male trans activist who thought atypical karyotypes like XXY were additional sexes.
By asking one simple question, I was able to change his mind.
Here’s how 🤓
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This cartoon is based on three false assumptions.
1) Basic biology defines sex as XX and XY.
- No, biology defines sex as the phenotypes that produce either sperm or eggs. Chromosomes hold the genetic instructions for sex development, but they are not sex itself.
2) There are
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@EdKrassen
When people say humans (and mammals in general) cannot change sex, they are scientifically correct.
Mammals are not sequential hermaphrodites. We are gonochoric, which means we are male or female for our entire life.
Changing sex is an evolved sexual strategy in certain
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@Variety
This is completely false. Here’s why.
There has been decades of research on the immense physical advantages males have over females, and transwomen are almost always typical males with no sex development disorder.
The strength difference between male and female bodies is vast.
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“Transwomen do not have a physical advantage over cis women."
This is false. Here’s why.
There has been decades of research on the immense physical advantages males have over females, and transwomen are almost always typical males with no sex development disorder.
The
Jonathan Van Ness: “The science that we have now says that transgender women do not hold an unfair biological advantage over cis women."
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Two gamete types = two sexes.
Sex is a duality, a pair. In other words, a binary.
Watch the full video here:
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I will say it again so we can drill this in: Caster Semenya does not have high testosterone due to his development disorder, 5-ARD.
Rather, he has high testosterone because of his sex, which is male. He has testes that produce male-typical levels of T, and that T androgenizes
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Why can't a male develop identical breasts to a female, since breast tissue growth is sensitive to high estrogen exposure in both sexes?
This has to do with what's called the hypothalamic-pituitary-gonadal axis, or HPG. This axis forms an important brain-to-gonad feedback loop
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The shedding of the uterine lining IS the period.
The cause is the hypothalamic-pituitary-ovarian (HPO) hormonal axis interacting with the uterus to induce the shedding. Only females can have this.
Bleeding and shedding your uterine lining is a SYMPTOM of your period, not the cause.
Your period is caused by your HORMONE levels, and the physiological effects they have on your body. Trans women hormone levels fluctuate on HRT just like cis women. We do in fact get periods.
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Why do high school boys consistently surpass the running times of elite Olympic female athletes? Why do males lift 30% heavier than weight-matched female counterparts?
Would love to hear the answer to these questions from gender activists.
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Menstruation is the shedding of the outer uterine lining (the stratum functionalis) through the vagina every month.
This involves a tightly orchestrated interaction between the pituitary gland, ovaries, and uterus.
So no, you most certainly do not.
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When people use the term "intersex," they are often describing all disorders that impact the development of the reproductive system. These disorders impact males or females. And it's this sex-specific knowledge that allows us to treat them accurately.
For example, you would call
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@IanCopeland5
@rohangilkes
Why don’t you address my scientifically accurate rebuttal instead of appealing to authority, which is a logical fallacy?
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From a peer-reviewed paper on male lactation: “We should therefore rethink what successful breastfeeding means. The main goal of lactation induction in transgender women may not necessarily be milk production, but rather the nonnutritional benefits that come from breastfeeding.”
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Cross-sex hormone use in females (high testosterone) has a host of detrimental effects to the body.
The tissues of the female reproductive system are organized around specific levels of estrogen and testosterone. When high levels of T are introduced consistently, ovulation is
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@EdKrassen
The male seahorse has the unique ability to incubate the fertilized egg in its pouch and provide it with nourishment, but it does not produce the egg. That is the job of the female.
Despite this unusual ability, the males are still defined as male because they produce the
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If “woman” means “anyone who identifies as a woman”, then what’s the word we can all use to refer to adult human females?
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Not being a *typical* male or female does NOT mean you’re not a male or female.
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During puberty, the reception of high levels of testosterone through the hypothalamic-pituitary-gonadal axis is critical for males. Block this axis, as puberty blockers do, and you'll end up with a host of physical and cognitive issues.
Researchers have tested the effects of
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Imagine thinking that one of the most fundamental, ancient biological phenomenon was created by men.
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Believing you are the opposite sex is in the same conceptual category as believing you are some other age, race, species, or any other characteristic that is immutable.
It should be treated as a psychological illness, not affirmed as true.
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@ZaqueoDeLeon
What exactly is backed up by science?
1. The idea that you can change sex?
This would require the differentiation of the gonads into the opposite sex, along with the reproductive anatomy to support it. This only happens in species who have evolved sequential hermaphroditism,
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What are the effects of blocking puberty in females?
Pubertal development in females requires the reception of sex hormones through the hypothalamic-pituitary-gonadal axis. Block this axis, as puberty blockers do, and you'll end up with a host of physical and cognitive issues.
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We do not all start out as females in the womb.
We all begin as males or females depending on our genetic profile, which determines the sex development path we will take. While we do all begin phenotypically indifferent (undifferentiated), this does not mean we're all female
@ncalimass
@cocteau8
@NewFifeRight14
@HavetStorm
@TheGayChrist
@sandyt0es
@TheFamousArtBR
@LouiseDistras
@Freda_Wa11ace
@joss_prior
@BertyJam
@firenicefly
@SusanFairweathe
@DavelnOz
Every foetus is conceived female ergo sex isn’t binary
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@ACLUofColorado
One's medically necessary because of life-threatening cancer. The other is entirely elective and not medically necessary because the trans identified patients requesting those surgeries have perfectly healthy bodies.
They have a psychological issue, not a physical one.
How is
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Sex has been binary for 1.2 billion years.
This won’t change anytime soon. 🤓
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No good data claims that 4% of the population is intersex unless you expand the definition so wide until it becomes meaningless, where even small variations in people’s physiology makes them “intersex.”
Are you a woman with slightly higher T? Congrats! You’re intersex now!
Let's start with some facts, which are likely underestimated:
At least 4% of the population is considered "intersex" in some way. So...it definitely isn't just a male/female world.
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Neil DeGrasse Tyson (
@neiltyson
) is misinformed and willfully ignorant on this topic.
He claims that Semenya is a genetic female with naturally high testosterone. But this is false.
Not only does Semenya have XY chromosomes, but also has "make-male" genes like SRY, which
In this new
@triggerpod
episode with
@neiltyson
, I am almost certain he is referring to South African runner Caster Semenya here.
If so, he is parroting mainstream misinformation about Semenya being a "female" with "naturally high testosterone." Semenya has XY chromosomes, and
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There is indeed one universal definition of male and female.
@spacemanfranko
@anniebannany69
@KatyMontgomerie
There's no simple male or female. If you can't read a chart, not my fault.
There's no such things as a single definition of "sex". It's a 5 dimensional variable, each of which are somewhere between male and female.
You said it's illiterate but actually, you just can't read.
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The Wikipedia article on "Sex" is currently under fire from activists trying to change it to include the "new, multifactorial definition of sex."
Here are some responses from Wikipedia users, including biologists, who disagree that the definition of sex must be changed.
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As I read more of the current neuroscience research in regards to gender dysphoria and transsexualism, it's becoming increasingly clear that trans individuals do not have sex-atypical brain structures, but rather that they have atypical structures involved in self-perception.
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On AGP and Phil Illy.
Autogynephilia is a sexual paraphilia that is linked to personality disorders like narcissistic personality disorder (NPD) and dangerous obsessive behaviors related to sexuality.
Typically those who have a paraphilia are not satisfied with keeping it to
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No one will ever make me stop talking about the scientific reality of male and female.
And to all the trans activists who comment on my posts trying to either make me stop posting or change my stances: good luck. You’re in a science-denying cult. Reality is not on your side.
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Only females can produce this incredible physiological feedback loop.
It requires the HPO (hypothalamic-pituitary-ovarian) axis along with the necessary extensive duct structures and the terminal duct lobular units (the clusters of spherical structures you see in the video).
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If we were met with “What about blind people?” every time someone defined what an eye is, we would know how absurd such a question is.
The same applies to “What about infertile people?”
Lack of present function in bodily systems does not call into question their existence.
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Imagine the delusional hubris it takes to believe you can overturn hundreds of million years of mammalian biology and change your sex.
Mammals are gonochoric. We remain male or female for life.
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The standard of evidence for trans activists is very low. They often just Google a claim and take as gospel whatever comes up first.
For example, this paper quoted below claims that human embryos all begin as female.
A quick look at the paper itself shows it’s from the 1970s,
@glitchinmetrix
@JanHunter2
@PoliticsPollss
Pet. you need to understand that gender and bio sex are two completely different things. some peoples gender aligns with their sex, some don’t. it’s really not that hard.
oh and about the embryos:
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Do those female lions with high T from ovarian tumors go from producing eggs to producing sperm? No, they do not.
Growing a mane or behaving more male-typical due to abnormally high T is not a sex change. It’s a change in secondary sex characteristics.
They remain female
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@EdKrassen
Yes, some species can change sex. This is known as sequential hermaphroditism, where an organism is able to change sex triggered by environmental circumstances.
Their gonads switch to the opposite type, and they produce the opposite sex gamete. This is common in certain fish
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@IanCopeland5
These fish switch from producing one type of gamete, the egg for instance, to producing the other type of gamete, the sperm. Or vice versa.
Their very cool system reinforces the binary definition of sexes.
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Sexes are defined by the difference in gamete size. Males produce sperm, females produce eggs.
“Intersex” people are either sterile or produce either sperm or eggs, and are therefore male or female. They do not produce a third gamete type and therefore are not a third sex.
@Tellmemore87
@Zingbing03
@minoc2
@JTTraveIs
@leftyvegan
@MrsPantsFace
Under biology intersex is considered outside male and female depending on the intersex person so it is technically a third sex.
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“I have a brain that mismatches my body” is like saying, “I have a heart that mismatches my body.”
Both the brain and heart are organs in your body. They are part of the body and integrated with it.
People who say this are practically saying, “My body mismatches my body.” A
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@IanCopeland5
@rohangilkes
I have a college-level education and graduated with honors. Though your elitist argument regarding credentials does not decide whether something is true or not.
I’ve studied sex differences extensively for seven years, worked closely with PhD level biologists, written 3 books
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Why do trans activists use people with congenital disorders, which have nothing to do with them, to argue that males can be females and vice versa?
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Females are not:
“Males with low T”
“Underdeveloped males”
“Males who didn’t masculinize”
Developing as a female in the womb is its own unique, gene-directed process that involves differentiation of specific structures and the maintenance of a specific physiology.
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Female bodies are not just “less testosterone.”
Male bodies are not just “more testosterone.”
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The amount of biologists on Twitter has risen 10,000% in the last few days.
Suddenly everyone seems to know what a woman is. It’s incredible 🤭
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There is a profound moral imbalance between prioritizing the feelings of a few men over the rights of women to fair and safe competition.
Why does even one man's feelings outweigh all women in sport?
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After controlling for sexual orientation, the authors found that the transgender participants had sex-TYPICAL structural brain connections.
The only difference was found in self-perception regions, regardless of sexual orientation.
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@MythinformedMKE
There's 5 lies that trans-identified male Veronica Ivy utilizes in this clip about biological sex and sport. Let's break it down.
1. "Policing whether transgender women and intersex women are really female is built in racism."
While there has been historical racism against
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The sex spectrum is one of the most popular forms of evolution denial that we’ve seen in recent times.
It claims that the sexes are constructed by society, and that there exists a continuum of options in between them.
To believe this, you’d have to deny many things, from how we
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What exactly is backed up by science?
1. The idea that you can change sex?
This would require the differentiation of the gonads into the opposite sex, along with the reproductive anatomy to support it. This only happens in species who have evolved sequential hermaphroditism,
Transexuality is backed up by science. And that is a fact in our world.
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READ: The Ugly Truth of Male Breastfeeding
In this detailed piece,
@shamanspirit13
analyzes the literature on artificially-induced male breastfeeding to see if it is safe and healthy for the infant.
Short answer: it’s not.
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I was taught in my Sociology of Gender class that drag is an exploration of how femininity is constructed and performed, that it helps breakdown sex stereotypes.
I think it does precisely the opposite. It makes a mockery of women while reinforcing and exaggerating stereotypes.
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Here are 7 reasons why this sex spectrum graphic by Scientific American is wrong.
🧵
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ABC News reported that Caster Semenya has a DSD causing "high testosterone levels." This is false.
5-ARD results in lack of DHT, which pauses the dev of external male genitalia.
The high T is not a product of the disorder; it is a product of Semenya's sex, which is male.
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'Stop Using Phony Science to Justify Transphobia' is another Scientific American article using the complexities of sex determination and the diversity of sex differences to argue that sex is not binary.
Let's talk about it!
THREAD (citations numbered)
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The male seahorse has the unique ability to incubate the fertilized egg in its pouch and provide it with nourishment, but it does not produce the egg. That is the job of the female.
Despite this unusual ability, the males are still defined as male because they produce the sperm,
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PCOS is not an "intersex" condition by any definition of the word.
PCOS is polycystic ovarian syndrome, and it results in unusual levels of androgen production in typical females.
"Intersex" is a misnomer umbrella term for conditions that result in sex ambiguity or a mismatch
@helen_a15
I mean- they ain’t wrong. PCOS is considered an intersex variation. It’s up to the individual to decide that for themselves. It’s not okay for one to dictate what others may choose for themselves. Tho I don’t agree with how this person worded their comment.
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Here is a comprehensive list of all the human sexes:
— Male
— Female
✌🏼
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I have a better proposal.
Do not give anyone drugs that will induce an endocrine disorder to treat a problem that is located not in the body but in the mind.
I have a proposal.
Instead of giving puberty blocker monotherapy to juvenile transsexuals, give them what they actually want: cross-sex hormones.
These could be administered instead of puberty blockers, or in combination.
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The idea that you can redefine an entire group of people (women, for example) to your own subjective whim, with no relationship to reality, is unbelievably narcissistic and delusional.
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On top of that, the paper describes the potential adverse effects on the infant of the drugs used to induce lactation, but says that we should also prioritize the validation of the trans woman’s identity.
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Gender activists consider hypospadias an "intersex" condition.
Hypospadias are the most common genital defect in newborn boys, which results in the urethra opening on the underside of the shaft, not the tip (the penis was not closed fully).
Can you imagine thinking this makes
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Many of the peer-reviewed papers praising breastfeeding in trans women are examples of how gender ideology has captured the research process.
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Cross-sex hormone use in males (female-typical levels of estrogen and testosterone) has a host of detrimental effects to the body.
The male body is organized around specific levels of testosterone and estrogen across development. When these are altered to female levels, a
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Male puberty happens because the hypothalamus tells the pituitary to produce luteinizing hormone (LH) and follicular stimulating hormone (FSH), which tells the testes to produce more testosterone. This creates a feedback loop between the hypothalamus, the pituitary, and the gonad
@Kimberfan76
@TMDawn12
@Tachardiella
@two_n_minus_one
@HelenWebberley
male puberty happens because of the Endocrine System - the Testosterone that is given to a trans boy to trigger physical puberty changes is the same testosterone that the testes release. that is what male puberty Is....
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@IanCopeland5
In two weeks, you’ve helped provide me with over 2000 new followers since you gave me the opportunity to use logic and evidence to debunk the false claims you were spreading. Your responses to me did not speak well of your knowledge.
I do appreciate the attention. Keep it up 🙏
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If you are going to read one scientific paper on biological sex, read this one.
It’s the best scientific summary for articulating why sex is binary, written in the peer-reviewed journal BioEssays.
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Do you not understand the science of the male performance advantage? The strength difference between male and female bodies is vast.
On average, males have:
- 57% more grip strength [1]
- 65% more leg strength [2]
- 90% more total upper body strength [3]
- 162% more punch
@Riley_Gaines_
Can you just address the reality and move past it? You sucked at swimming. That's why you lost.
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Sexes are defined by the difference in gamete size. Males are the sex that produce sperm, and females are the sex that produce eggs.
“Intersex” people are either sterile or produce either sperm or eggs, and are therefore male or female. They do not produce a third gamete type
Not everyone is born either male or female.
In the
#UnionofEquality
everyone has the right to be exactly who they are.
#EU4LGBTIQ
on
#InterSexAwarenessDay
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It is good this paper recognizes that sex plays a fundamental role in sports performance advantage, but they make one glaring error in their mention of “intersex.”
They claim that “intersex” makes up 2% of the population. The clinical usage of “intersex” refers to conditions
Biological sex is a primary determinant of athletic performance because of fundamental sex differences in anatomy and physiology dictated by sex chromosomes and sex hormones.
Statement available in
@TJACSMonline
and
@MSSEonline
Paper & resources:
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Transgender people do not have a mismatch of chromosomes and phenotype or ambiguous sex characteristics.
They are born as typical, healthy males or females with no reproductive disorder.
@IsobelSGray
Blow their minds and tell them "Intersex". Actually, I've heard a very good case that transgender people ARE Intersex.
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The word “woman” exists for a simple yet profound reason: it’s the name for the adult female of the human species.
We’re always going to need a word that describes this group of humans.
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Guess what happens in say, weightlifting, when you sort men and women by weight class?
The men can still lift 30% more, even at the same weight. That’s because the male performance advantage is far deeper than just weight or height.
@stormrobinson
@AriDrennen
So that's a sexist and antiquated tradition. A more appropriate method is via weight classes and builds, if you really want to talk about trying to level the playing field. But that would most definitely imply mixing cis and trans gender athletes across the board. That's facts.
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